An electromagnetic control device of that type can be an actor. Other terms commonly used in control technology for an actor are actuator, control motor and/or lifting magnet. Such a component serves, for example, for driving or moving valves or flaps to control the flow of gaseous or liquid media. A possible field of use in this case is automotive technology.
For accurately timed actuation of the control device a knowledge of the position of the control element, or the armature which is part of the control element, is often important.
DE 10 2008 043 340 A1 describes a method for detecting the position of an armature of an electromagnetic actuator, which is arranged to move between two coils. The use of two coils with an intermediate space within which the armature moves entails providing a relatively large fitting volume.
Furthermore, DE 42 25 968 A1 describes a method for contactless displacement measurement. A measuring coil with a number of voltage tapping points arranged one after another in the longitudinal direction is provided. The coil is surrounded by an electrically or magnetically conducting, annular measurement object. This ring can be displaced outside and over the coil in its longitudinal direction. Its axial dimension is at most as large as the distance between two of the coil's tapping points. It consists of a material with low specific electrical resistance, such as aluminum. In particular because of this preferred choice of material, the measurement method cannot easily be converted for determining the position of a longitudinally movable, ferromagnetic armature of an electromagnetic control device.
In other known methods for detecting the position of the armature of a control device the control element is connected mechanically by way of a sensor tappet rod to an external position sensor of virtually any desired type. This again requires a relatively large fitting volume. In many applications, moreover, the space needed for the external position sensor is not available.
Furthermore, embodiments of control devices are also known which comprise a sensor coil intended exclusively for measurement purposes. The measurement coil can be arranged in the inside space of the main coil provided for displacing the position of the armature, coaxially with the main coil. Thus, the inside coil space of the main coil must provide extra space for the separate sensor coil, and this increases the overall fitting volume of the control device.